This invention relates generally to a tool for handling small parts and more particularly to improvements in hand held, pneumatically operated implements for picking up, placing, adjusting, or removing delicate or sensitive parts such as an electronic microelement to be affixed and connected to a circuit board or a larger integrated circuit chip to be affixed and connected with its many solder points to a circuit board.
In the development of modem microelectronics, the various elements and components incorporated into the assembly of a circuit as, for example, in a microprocessor, a computer, or controls for automated apparatus, have typically become smaller, more delicate and sensitive, more costly, and very critical in their exact placement, as on a circuit board, during assembly or manufacture or testing or repair or replacement. Consequently, it has become increasingly difficult, for example, to successfully and efficiently select a small part, pick it up, place it precisely, hold it during a soldering or other securing process, and then release it--all without placement or orientation error and without subjecting the part to unacceptable mechanical, thermal, or electrical stresses.
Prior art efforts have typically been directed toward mechanical holding techniques such as clamps, forceps, tweezers, or the like; and in some applications such approaches are satisfactory. However, holding a small part by mechanical measures have disadvantages of lack of reliability or of the part slipping away and being dropped. Further the mechanical stress caused by the tweezer compression can, for delicate parts, be intolerable. Further, such tools suffer a lack of versatility in exactly how and in what orientation it selects and picks up the part.
One non-mechanical approach has been to provide a hand held tool containing a spring loaded piston creating a vacuum chamber between the interior of the tool and a suction cup affixed to the nozzle end of the tool. When a part is to be picked up, the piston is pushed forwardly by a plunger or trigger toward the nozzle, the part is placed against the suction cup, and the piston released to create a holding vacuum by the spring. When the part is to be released, the plunger or trigger is again pushed forwardly to extinguish the vacuum within the chamber and the holding suction cup. Another version of this technique is to provide instead of a spring loaded piston within the chamber, a fountain pen type elongated bladder which is compressed by a trigger holding a vane against the side of the bladder to create a vacuum. Again, when the part is to be released, the vane against the bladder is pushed inwardly by the trigger and the holding vacuum is extinguished.
These prior art vacuum devices suffer from at least three limitations which for many modem applications constitute serious disadvantages: first, there is a limit to the magnitude or volume of the vacuum available due to the geometry of the piston chamber or bladder; second, some leakage is inherent and thus the holding time for such a device is limited such that its holding force is not constant, diminishes, and at an unknown moment the part may be released and dropped; third, the necessity of "working" the piston to extinguish the holding vacuum may cause an unacceptable recoil or other displacement of the part just as it is being critically emplaced. This type of holding device is well described in U.S. Pat. No. 5,106,139, issued to H. D. Palmer on Apr. 21, 1992 and entitled HAND-HELD PICK-UP DEVICE.
The prior art also includes hand held implements which utilize an external source of compressed air to generate holding forces as by "suction cup" or venturi effects. For a description and discussion of this class of holding devices and their development see Applicant's U.S. Pat. No. 5,928,537 issued Jul. 27, 1999, entitled PNEUMATIC PICKUP TOOL FOR SMALL PARTS and its pending divisional application Ser. No. 09/359,451 filed Jul. 22, 1999, now U.S. Pat. No. 6,043,458, entitled "PNEUMATIC ROTATABLE HAND HELD PICKUP TOOL".
It is an object of the present invention to provide a pickup or holding implement which is not subject to the above and other disadvantages and limitations of the prior art.
It is another object to provide such a tool which while being very light and compact can create and maintain a vacuum generated high magnitude holding force for an unlimited time and yet be released instantly and without displacement when desired.
It is another object to provide such a tool which in operation does not suffer recoil or other deleterious reaction effects.
It is another object to provide such a tool which may supplement or boost the holding effects of a fixed vacuum shop line.
It is another object to provide such a tool which may create and maintain a "reservoir" of vacuum for providing holding effects instantly on demand.
It is another object to provide such a tool which is rugged, reliable, simple to operate and maintain, and which is inexpensive to manufacture.
It is another object to provide such a tool which is versatile with respect to the proper and effective handling of very small, very large and heavy, pressure or distortion sensitive, or high temperature parts.